Heretofore, performed is a surface finishing of a workpiece, such as deposition, nitriding or impregnation, contained in a chamber maintained in a depressurized or vacuum state, by use of PVD or CVD process. In a processing apparatus for performing modification processing such as deposition by use of such PVD or CVD process, it is often performed to finely set a temperature of a workpiece during the processing depending on mechanical properties, adhesion, etc. For example, for enhancing adhesion property between a deposited film and a substrate, they say it is desirable to set the processing temperature to a relatively high value. Meanwhile, from a viewpoint of mechanical properties, there can be a case where setting the temperature of the workpiece to a relatively low value is rather advantageous. That is why the processing temperature of the workpiece, in the PVD or CVD process-based processing, is finely determined depending on mechanical properties, adhesion, etc. This processing temperature requires accurate measurement of a real temperature of the workpiece during the processing.
Other than deposition by PVD or CVD process, the deposition using the processing apparatus as a heating furnace to heat a workpiece, may require a fine temperature management. This case also requires the real temperature of the workpiece to be an accurately measured.
As a technique for the measurement of a real temperature of a workpiece, the following means have been known.
The following Patent Literatures 1 and 2 disclose a measurement method including providing an outer wall of a chamber with a window allowing an inside of the chamber to be visually recognized at a position outside the chamber, and actually measuring a real temperature of a workpiece in the chamber through the window with an infrared radiation thermometer disposed outside the chamber.
The following Patent Literature 3 discloses a method performed in an apparatus for deposition on a surface of a plate-shaped workpiece, the method including bringing a contact-type thermometer into contact with a reverse-side surface of the workpiece on a side opposite to an obverse-side surface thereof on which the deposition is performed, and calculating a real temperature of the workpiece during the processing, from the measured temperature. Such a contact-type thermometer also enables the real temperature of the workpiece to be actually measured.
The following Patent Literature 4 discloses a method including measuring an atmosphere temperature in a heating zone surrounded by a heat insulating material, in order to measure a temperature of the heating zone. The method described in the Patent Literature 4 is not for measuring a temperature of a workpiece during processing but for judging degradation of a thermocouple based on the atmosphere temperature; however, it is suggested that the atmosphere temperature can be utilized as substitute for a real temperature of the workpiece.
The following Patent Literature 5 discloses a method of measuring a temperature of a workpiece composed of a silicon wafer substrate, in a production process with use of vacuum or low-pressure plasma, such as a CVD or sputtering process. This method includes: forming, on a substrate as a workpiece, a thin film made of a polymeric material allowing the thin film to have a variable shape depending on temperature and measuring a temperature of the workpiece during processing, based on the shape variation in the thin film.
The conventional techniques described in the Patent Literatures 1 to 5, however, have the following problems.
The method using a radiation thermometer as described in the Parent Literatures 1 to 2 allows a temperature value measured by the radiation thermometer to be undesirably varied along with a change in emissivity of a surface of a workpiece as a measurement target. This means that a radiation thermometer enables the temperature to be measured only in the case of stable surface. Hence, regarding a workpiece having surface physical property or surface state variable along with a progress of processing as in the above deposition processing, unstable emissivity of the surface of the workpiece may prevent the measurement of the temperature from being performed with a high degree with the radiation thermometer. Moreover, there exists a member other than the workpiece in the chamber, the member also emitting infrared rays, which is likely to cause a large error in a result of the measurement of the real temperature by the radiation thermometer.
Furthermore, in a processing apparatus for deposition, a deposition material adheres also to the observation window, and infrared lays having passed through the window on which the deposition material is adhered are measured by the radiation thermometer. This situation includes a possibility that the deposition material adhering to the window varies intensity (energy amount) of the infrared lays to be measured. This may prevent the real temperature of the workpiece from being accurately measured and may cause a large error in temperature measured by the radiation thermometer.
The measurement method by use of a contact-type thermometer as in the Patent Literature 3 is intended for a workpiece statically placed inside a chamber, in principle. With this measurement method, which uses a contact-type thermometer, it is difficult to measure the temperature of the workpiece during the processing because the contact-type thermometer cannot be kept in contact with the moving workpiece placed on a turntable or the like. Therefore, it is not realistic to employ the measurement technique described in the Patent Literature 3 in a CVD or PVD process which generally involves turn and/or revolution of a workpiece.
Besides, PVD process such as arc ion plating is sometimes performed by providing a potential difference between a chamber and a workpiece. This requires a thermocouple and means for extracting an output signal of the thermocouple with electrical insulation of the output signal from the chamber for insertion of the contact-type thermometer into the chamber from outside to bring it into contact with the workpiece, thus significantly complicating the structure of the processing apparatus.
The method including measuring an atmosphere temperature as in the Patent Literature 4 cannot be employed except the case where the relationship between a temperature (real temperature) of a workpiece and the atmosphere temperature has been accurately figured out during processing. In the case of constant condition of a shape or process or the like of a workpiece, the real temperature of the workpiece can be accurately calculated from the atmosphere temperature; on contrary, in the case of inconstant condition and the like of a shape or process of a workpiece, the real temperature of the workpiece cannot be accurately calculated from the atmosphere temperature.
The method described in the Patent Literature 5, including extracting the thin film outside a chamber and determining a history of temperature change based on the change in the shape of the extracted thin film, is incapable of continuous measurement of the real temperature of the workpiece during processing.